Pulmonary Function Tests in Thunderstorm-associated Respiratory Symptoms: A Cross-sectional Study.

Background: Epidemic thunderstorm asthma is an observed increase in cases of acute bronchospasm following thunderstorms. This study aimed to compare the frequency of obstructive airway disease or bronchial hyperresponsiveness in subjects with thunderstorm-associated respiratory symptoms with subjects with similar symptoms presented at other times. Methods: A cross-sectional study from June to November of 2013 was conducted on subjects with thunderstorm-associated respiratory symptoms living in Ahvaz City, Iran. Thunderstorm-associated subjects were presented with asthmatic symptoms in thunderstorms, and other patients presented with similar symptoms at other times. Baseline spirometry was performed on patients to examine the presence of obstructive airway disease. In all patients with normal spirometry, a provocation test was applied. A comparison of qualitative and quantitative variables was made using the Chi-square and independent t test, respectively. All analyses were carried out using SPSS Statistics Version 22. A P value less than 0.05 was considered statistically significant. Results: Out of 584 subjects, 300 and 284 participants were in thunderstorm-associated and non-thunderstorm-associated groups, respectively. After the final analysis, 87 (30.6%) and 89 (33.3%) of the thunderstorm-associated subjects and non-thunderstorm-associated group, respectively, had pieces of evidence of airflow limitation (P=0.27). Among the patients with normal spirometry, 161 (81.72%) of the thunderstorm-associated patients and 100 (56.17%) patients of the non-thunderstorm-associated symptoms group had a positive methacholine challenge test result (P<0.001). Conclusion: Most of the patients with thunderstorm-associated respiratory symptoms had no obvious evidence of airflow limitation in spirometry.

Forced Expiratory Flow at 25-75% as a Marker for Airway Hyper Responsiveness in Adult Patients with Asthma-like Symptoms.

BACKGROUND: The aim of the present study was threefold: to assess the association between baseline FEF25-75 and Airway Hyper-responsiveness (AHR), to specify whether a decrease in FEF25-75 may reflect severe hyper-responsiveness, and finally to confirm a FEF 25-75 cut-off value. MATERIALS AND METHODS: In a cross sectional study in Imam Khomeini Hospital, Ahvaz, patients suffering from respiratory symptoms due the 2013 autumn rainfall with normal FEV1 and FEV1/FVC were evaluated by methacholine challenge test. Those with PD20<1000, 10002000 µg were classified as severe, moderate and mild AHR, respectively. Data were analyzed using Chi-square, Independent t-test, One-way ANOVA and Receiver Operating Characteristic (ROC) curve. RESULTS: Among the 234 patients, mean baseline FEF25-75 was 84.2±22.7% for 54 patients having a negative bronchial provocation test result and 70.9±19.2% for 179 patients with a positive bronchial provocation test result (P < 0.0001). No change was observed in the median PD20 among patients with a higher baseline FEF25-75. ROC analysis showed that FEF25-75 could potentially be a predictor of AHR, but it could not confirm the cut-off value of FEF25-75 for these patients. CONCLUSION: When asthma begins, AHR could be predicted by impaired FEF25-75 with normal FEV1 and FEV1/FVC. However, we could not determine a cut-off value, and no association was found between a greater impairment of FEF25-75 and a more severe AHR.